Electrosurgical system for measuring contact quality of a return pad

ABSTRACT

A return pad includes a backing, at least one return electrode, and at least one ring sensor. The backing has a top side, a bottom side, and a periphery. The return electrode is disposed on the bottom side of the backing layer and is adapted to connect to a current generator. The ring sensor(s) is disposed in substantial concentric registration with the periphery of the backing and is configured to connect to a measuring component. The measuring component is operable to approximate contact quality of the return electrode during electrosurgical application and is configured to communicate with the generator.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Divisional of U.S. patent application Ser. No.11/800,687, filed May 7, 2007, now U.S. Pat. No. 8,080,007, the entiretyof which is incorporated by reference herein for all purposes.

BACKGROUND

1. Technical Field

The present disclosure relates to an electrosurgical return pad, andmore particularly, the present disclosure relates to an electrosurgicalreturn pad with contact quality monitoring for use duringelectrosurgery.

2. Background of Related Art

Electrosurgery is the application of electricity and/or electromagneticwaves to cut or modify biological tissue during a surgical procedure.Generally, electrosurgery utilizes an electrosurgical generator, areturn electrode, and a source electrode. The electrosurgical generatorproduces an electromagnetic wave, typically above 100 kilohertz, betweenthe return and source electrodes when applied to tissue. Theelectromagnetic wave created therebetween dissipates energy as heat asit travels from one electrode to the other. Electromagnetic frequenciesabove 100 kilohertz are employed to avoid muscle and/or nervestimulation.

During electrosurgery, current generated by the electrosurgicalgenerator is conducted through patient tissue between the twoelectrodes. The current causes the tissue to heat up as theelectromagnetic waves overcome the tissue impedance. Although, manyother variables affect the total heating of the tissue, usually withmore current density, increased heating results. Current can be used forcutting, dissection, ablation, arresting blood loss and coagulation, andare well-known.

The two basic types of electrosurgery employed are monopolar and bipolarelectrosurgery. Both types use an “active” and a “return” electrode,although the distinction is not always necessary. In bipolarelectrosurgery, the surgical instrument has an active electrode and areturn electrode on the same instrument or in very close proximity,usually causing current to flow through a smaller amount of tissue. Inmonopolar electrosurgery, the return electrode is located elsewhere onthe patient's body and is usually not part of the surgical instrumentitself. In monopolar electrosurgery, the return electrode is part of adevice referred herein as a return pad.

The return pad is intended to lower the current density in nearby tissuewhen current flows between the return pad and the patient's tissue. Thecurrent density through the tissue near the return pad is related to theimpedance between the tissue and the return pad. This impedance isreferred to herein as contact impedance. When the surface area of thereturn electrode contacting the skin is reduced, increases in currentdensity may heat tissue up to the point of possibly causing skin damage.Maintaining low contact impedance helps prevent electrosurgery relatedinjuries.

Generally, resistive electrodes tend to have more uneven heating thancapacitive electrodes. Because electricity tends to conduct through thepath of least resistance, more current tends to conduct through thetissue near the edge of a resistive electrode that is closest to theactive electrode, creating more localized heat. This is known as the“edge effect”. Although, capacitive electrodes tend to have more uniformheating than resistive electrodes, measuring contact quality has beenmore difficult.

SUMMARY

The present disclosure relates to an electrosurgical return pad, andmore particularly, the present disclosure relates to an electrosurgicalreturn pad with contact quality monitoring for use duringelectrosurgery.

In one embodiment, the return pad includes a backing, at least onereturn electrode, and at least one ring sensor. The backing has a topside, a bottom side, and a periphery. The return electrode is disposedon the bottom side of the backing layer and is adapted to connect to acurrent generator. The return electrode may be capacitive or resistive;and the ring sensor may be capacitive or resistive. The ring sensor maybe disposed in substantial concentric registration with the periphery ofthe backing. Additionally or alternatively, the ring sensor may bedisposed in substantial vertical registry with the bottom side of thebacking layer. The ring sensor may also be configured to connect to ameasuring component. The measuring component is operable to approximatecontact quality of the return electrode during electrosurgicalapplication and may be configured to communicate with the generator.

In another embodiment, the ring sensor may include two partiallyconcentric ring electrodes configured to cooperate with the measuringcomponent. The ring sensor can measure contact quality during an electrosurgical procedure and communicate contact quality to the generator. Thetwo ring electrodes may be disposed in substantial vertical registrywith the return electrode.

In yet another embodiment, a patient interface material may be disposedbetween the backing layer of the return pad and skin. The patientinterface material may also be configured to facilitate contact qualitymonitoring of the return electrode. The interface material may include aconductive gel, a conductive adhesive, an insulating gel, an insulatingadhesive, a dielectric gel, a dielectric adhesive, an insulator, and/orsome combination thereof. The ring sensor may include a temperaturesensitive material that may be configured to sense contact quality basedupon temperature, e.g., a positive temperature coefficient ink.

In another embodiment a control component of the generator may beutilized; and the measuring component may be configured to receive andprocess sensor data and relay the sensor data to the control component.The return electrode may be configured to electrically isolate thereturn electrode from the generator when the measurement componentdetermines that a threshold condition has been reached. Additionally oralternatively, the return pad may include an intelligence component thatmay be configured to process sensor data and analyze the data with arisk function algorithm.

In yet another embodiment, a method for monitoring contact quality of areturn pad described above is disclosed. The method includes the stepsof: providing a return pad; activating at least one ring sensor of thereturn pad to operatively communicate with a measuring component; andapproximating the contact quality of the return electrode by analyzingcapacitance, impedance and/or resistance from the at least one ringsensor. The methodology may further include the step of electricallyisolating the return electrode of the return pad from a generator whenthe measuring component determines that a threshold condition has beenreached.

In another embodiment, an electrosurgical system for measuring contactquality of a return pad is discussed. The system includes a return pad,a return interface and a sensing interface. The return pad includes abacking layer, a first capacitive electrode and a second capacitiveelectrode. The first and second electrodes may be disposed on thebacking layer. The return interface may be adapted to return current forthe first and second capacitive electrodes. The sensing interface may beoperatively coupled to a generator and configured to monitor theimpedance between the first and second capacitive electrodes todetermine contact quality. Additionally or alternatively, the sensinginterface is operatively coupled to a generator and is configured tomonitor a return current difference between the first and secondcapacitive electrodes to determine contact quality.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the subject instrument are described herein withreference to the drawings wherein:

FIG. 1A is a schematic bottom-view of a return pad according to oneembodiment of the present disclosure showing two ring electrodesdisposed in substantial concentric registration with the periphery ofthe backing;

FIG. 1B is a schematic cross sectional view along line 1B-1B of thereturn pad of FIG. 1A;

FIG. 2 is a schematic bottom view of another embodiment of the presentdisclosure showing a return pad having a ring sensor with a distal endhaving a break point in accordance with the present disclosure;

FIG. 3A is a schematic bottom view showing a return pad having twoconcentrically aligned ring electrodes in accordance with the presentdisclosure;

FIG. 3B is a schematic cross sectional view along line 3B-3B of thereturn pad of FIG. 3A;

FIG. 4 is a schematic bottom view showing a return pad having a ringsensor in substantial vertical registry with the return electrode inaccordance with the present disclosure;

FIG. 5A is a schematic bottom view showing a return pad that utilizes aring sensor with a single ring electrode in accordance with the presentdisclosure;

FIG. 5B is a block diagram illustration of the impedances associatedwith the return pad of FIG. 5A;

FIG. 6A is a block diagram illustrating a system that has two capacitivereturn electrodes for measuring contact quality in accordance with thepresent disclosure;

FIG. 6B is a block diagram illustrating a system that has two capacitivereturn electrodes for measuring contact quality by utilizing a sensinginterface configured to monitor a return current difference between twocapacitive return electrodes in accordance with the present disclosure;

FIG. 7 is a block diagram of an electrosurgical system utilizing areturn pad having a ring sensor and a return electrode in accordancewith the present disclosure; and

FIG. 8 is a flow chart showing one particular method in accordance withthe present disclosure.

DETAILED DESCRIPTION

The embodiments that follow are described with reference to the attacheddrawings. Like reference numerals are used to refer to like elements,steps or features but are not intended to indicate identical features.The word “component” is used herein to refer to an entity that relatesto and/or utilizes hardware, software, circuitry, transducers, amicroprocessor, a microcontroller, software in execution, or somecombination thereof. The term “impedance” is not intended to limit, butrather is to describe the natural phenomenon of a material's oppositionto a wave as the wave propagates through the material, where the type ofwaves included are electromagnetic waves, electrical waves, electricitywaves, RF waves, AM-frequency waves, FM-frequency waves, microwavewaves, or any other wave of oscillating electrical charge or magneticfield. In addition, the term “current” is used herein to describe theflow of electrical charge.

Turning to FIGS. 1A-5, several embodiments of the present disclosure areshown that utilize a ring sensor. FIGS. 1A-4 are schematic views of areturn pad that includes a ring sensor having two electrodes while FIGS.5A and 5B show a ring sensor that has one electrode.

Referring initially to FIG. 1A, a return pad 100 is shown that includesa backing 102 (FIG. 1A-5) that supports a return electrode 104 (FIGS.1A-5). Backing 102 has a ring sensor 110 disposed in substantialconcentric registration with the periphery of backing 102 as shown byFIGS. 1A-5A with two electrodes 106 and 108 or may have a ring sensor508 with one electrode 506.

The backing 102 may be made of cloth, cardboard or any other material tofacilitate return pad operation. The return electrode 104 may be madefrom materials that include aluminum, copper, mylar, metalized mylar orother suitable conductive material. Electrode 104 may also include aninsulator, glue, adhesive, gel or other material that is configured toattach the return electrode 104 to tissue. Return electrode 104 mayadditionally include a dielectric, insulator or other materialpositioned between a conductor and tissue to enhance capacitiveproperties of the return electrode as explained in more detail below.

As mentioned above, ring electrodes 106 and 108 form ring sensor 110(FIGS. 1A-5) while ring electrode 506 forms ring sensor 508 (FIG. 5A).The term “ring” is not meant to define a circle, arc, or other shape,but is intended to indicate any shape possible to measure the impedanceof a given contact area of a return pad 100, 200, 300, 400 or 500. Ringsensor 110 or 508 may also include an insulator, glue, adhesive, gel orother suitable material to attach return electrode 104 to either backing102 and/or to tissue. Additionally ring sensor 110 may be electricallyisolated from return electrode 104.

One example of use of a return pad 100 according to the presentdisclosure includes a return electrode 104 in a capacitive configurationwith ring sensor 110 in a resistive configuration. In this example, RFenergy can return through 104 while concurrently having an oscillatingcurrent between ring electrode 106 and ring electrode 108 to produce acurrent through contacting tissue approximately below return electrode104. If the center portion of return pad 100 starts tenting (i.e.,starts peeling away from the skin), the impedance measurement from ringelectrode 106 and ring electrode 108 may increase. If a rise inimpedance is significant enough, generator 516 (see FIG. 7) measuresthis change in impedance and may trigger an event, e.g., an alarm, awarning, and/or may prevent any therapeutic current from flowing until asafe impedance level exists.

Turning now to the more detailed depiction of a return pad 100 in use,FIG. 1B is a cross section view of return pad 100, along axis 1B-1B,contacting skin barrier 114. Return pad 100 also includes an interfacematerial 116 disposed between ring electrode 108 and skin barrier 114,an interface material 118 disposed between return electrode 104 and skinbarrier 114, and an interface material 120 disposed between ringelectrode 106 and skin barrier 114.

Current arrows 122 depict current traveling through the skin barrier 114and interface material 118. Current arrows 124 depict current travelingthrough the skin barrier 114 and interface material 120; and currentarrows 126 depict current traveling through the skin barrier 114 andinterface material 116. Current arrows 128 and 130 depict currenttraveling between ring electrodes 106, 108 and interface materials 120,116, respectively. Current arrows 132, 134 depict current travelingbetween interface materials 120, 116, and 118 and current arrows 136depict current which may travel between return electrode 104 andinterface material 118.

Interface materials 118, 120, or 116 may be conductive, insulating,dielectric, or can have any other electrical property. Additionally oralternatively, interface material 118, 120, or 116 may provide adhesionor temperature dependent properties. In another embodiment, there may beelectrical insulation (including air) between interface material 118 and116 and/or between interface material 118 and 120 (not shown in thisconfiguration). Adding insulation and/or an air gap between interfacematerials 118 and 116, and/or between interface materials 118 and 120 toreduced current arrows 134 and 132, respectively, may increase thesensitivity of ring sensor 110.

A measuring component 706 (FIG. 7), may be operatively coupled to ringsensor 110 to measure the various impedances of the return pad 120.These impedance measurements may be conducted utilizing current invarious ways. For example, by changing frequency, voltage, wattage, oramperage one skilled in the art can make an approximate impedancemeasurement. Applying a voltage differential across ring electrode 106and ring electrode 108 will produce current 130 and current 128. Current128 can either flow through skin 114 to produce current 124, or throughinterface material 118 to produce current 132. In addition, current 130can flow either through skin 114 to produce current 126 or to interfacematerial 118 to produce current 134. If return pad 100 starts to have areduced contact with skin 114, current 124 and current 126 will changebased upon changing impedance. A change of impedance thus reflects achange in return pad contact with tissue 114.

One way to effectively approximate impedance is to assume that impedanceZ₀ is defined as the impedance from ring electrode 106, throughinterface material 120, through interface material 118, throughinterface material 116 and to ring electrode 108. Also, assume thatimpedance Z₁ is defined as the impedance from interface material 120through skin 114 and then through interface material 116. In this case,the total impedance, Z_(total) measured by ring sensor 110 isapproximately the impedance of Z₀ in parallel with Z₁. Thus, therelationship is described as Z_(total)≈Z₀∥Z₁. Any change of contactimpedance from interface material 120 and skin 114 or interface material116 and skin 114 would thus have an impact of Z_(total) and ismeasurable. By utilizing various conductive and insulating materials, itis possible to keep impedances approximately constant (in this example,Z₀) so that the impedance being measured (in this example Z₁) can bemore accurately ascertained.

Measuring component 706 (see FIG. 7) may be configured to take intoaccount current produced by return electrode 104 and that suitablesignal conditioning can be employed to account for this current. Also,ring electrode 106 and ring electrode 108 may employ the use of atemperature dependent material so that changes in temperature arereflected in an impedance measurement.

As shown in FIGS. 1A and 2, the area between ring electrode 106 and ringelectrode 108 is configured to approximate the contacting area of thepad 100 to skin 114. Contrast this to FIG. 3A that has electrodes 106and 108 configured to measure contact quality near the periphery ofreturn electrode 104. The general shape of ring sensor 110 may vary inorder to effectively measure the contact quality of various portions ofa return pad.

Turning now to another ring sensor 110 configuration of the presentdisclosure, FIG. 2 depicts a return pad 200 having a backing 102 with areturn electrode 104. Return electrode 104 may be in a resistiveconfiguration or in a capacitive configuration. A first ring electrode106 and a second ring electrode 108 form ring sensor 110. Ring sensor110 may be capacitive or resistive. Ring sensor 110 is disposed insubstantial concentric registration with the periphery of backing 102.Current (not shown) exits return pad 200 via connector region 214. Breakpoint 216, depicted as a dashed-lined oval, is the general region wherering electrode 106 and ring electrode 108, if connected, would have madering sensor 110 a single electrode. Ring return region 218, alsodepicted as a dashed-line oval, is the general area where the ringsensor 110 signal exits return pad 200. A ring sensor reading may betaken from ring return region 218 either directly or indirectly with theaide of an electrical conductor and/or waveguide for further analysis(see FIG. 7, waveguide 716). The term waveguide includes but is notlimited to: a coaxial cable, a conductor, a plurality of conductors, aninsulator, a dielectric, shielding, cabling, connectors, or somecombination thereof.

Electrical current is depicted in FIG. 2 as if the pad were contactingtissue or if a conductive material were present. Current arrow 220 is arepresentation of the majority of the current flowing between ringelectrode 106 and ring electrode 108. Current arrow 222 depicts currentflowing from ring electrode 108 and ring electrode 106 near break point216 and current arrow 224 depicts current flowing from electrode 108 andring electrode 106 near exit point 218.

A measuring component 706 (see FIG. 7), can produce a current utilizingring sensor 110 to measure impedance. As the return pad contacts tissuebarrier 114, currents 220, 222, and 224 can change based upon return pad200's contact with tissue barrier 114. Respective changes in currents220, 222, and 224 may be dependant upon geometry, interface material andother variables. For example, measured impedance may be more responsiveto changes in contact impedance around break point 216. Thus it may beadvantageous to change the geometry, material used, or thickness of ringelectrode 106 or ring electrode 108 near break point 216 to accommodatefor this abnormality. It may be advantageous in certain circumstances toconfigure certain portions of the ring electrode to have increased orreduced areas of sensitivity depending upon a particular purpose. Aninterface material (not shown in FIG. 2 with return pad 200) may beincluded to modify ring sensor's 110 signal or the return currentthroughout return pad 200 and/or may aide in securing return pad 200 totissue and/or skin.

Although return pad 200 is depicted as having a connector region 214near ring return region 218, the connector region 214 may not be locatedon the same portion or near each other on return pad 200, i.e., the ringsensor signal may exit from any location on or near return pad 200.Additionally or alternatively, the return signal may exit return pad 200from any location as well depending on a particular pad 200configuration. Break point 216 may also be located at any position onreturn pad 200.

FIGS. 3A and 3B show another embodiment of the present disclosure havinga return pad 300 that facilitates peeling detection and has a ringsensor 110 in a different configuration than in FIGS. 1A-2. Return pad300 includes a backing 102 made of any material as described above thatprovides support for return pad 300. Ring electrode 106 and ringelectrode 108 again are configured to form ring sensor 110. And ringsensor 110 may be capacitive or resistive.

Ring electrode 106 and ring electrode 108 are disposed in substantialconcentric registration with the periphery of backing 102. Electrode 104is disposed relative to ring electrode 106 and 108 in a generallyconcentric fashion, which is configured to facilitate peel detection.The impedance measurement taken from ring sensor 110 is primarily afunction of contact impedance between ring electrode 106 and ringelectrode 108. Any edge peeling would affect the measured impedance thusallowing measuring component 706 (see FIG. 7) to measure this effect.

FIG. 3B shows a cross sectional view of FIG. 3A along line 3B-3B. Ringelectrodes 108, 106 and return electrode 104 interface with skin barrier114 through interface material 314, 316 and 318, respectively. Currentarrows 320 depict current crossing the barrier between ring electrode108 and interface material 314. Current arrows 322 depict current thatcrosses the return electrode 106 and the interface material 316 barrier,and current arrows 324 depict the current that crosses the returnelectrode 104 and interface material 318 barrier. Current arrows 326depict current crossing the barrier of interface material 314 and 316,and current arrows 328 depict current crossing the barrier of interfacematerial 316 and 318. Interface material 314/skin barrier 114, interfacematerial 316/skin barrier 114, and interface material 318/skin barrier114 show current arrows as 330, 332 and 334, respectively. Interfacematerials 314, 316, and 318 are not necessary or critical and may eitherbe an adhesive or gel and may be either insulating or conductive. In yetanother configuration, there may be an insulator (including air) betweeninterface materials 314 and 316 (not shown) causing current (representedby arrows 326) to be reduced. The reduction (or elimination) of currentrepresented by current arrows 326 may increase the sensitivity of ringsensor 110.

Return pad 300 is shown as contacting skin barrier 114 and illustratesthe effects that an edge peel would have on an impedance measurement inthis configuration. To measure impedance, a DC or AC signal may beapplied across ring electrode 108 and ring electrode 106 to produce acurrent. An analysis of the current 320 and/or 322 can be the basis formonitoring contact quality. For example, if interface material 314partially peeled away from skin 114, then the impedance across the 314interface material/skin barrier 114 would increase and a larger voltagewould be necessary to maintain the previous current levels of current320 and/or current 322. This increase in voltage would correspond to anincrease in contact impedance, which would be recognized by theelectrosurgical unit 702.

FIG. 4 shows another embodiment of the present disclosure having areturn pad 400 that also facilitates peeling detection and has a ringsensor 110 in a different configuration than in FIGS. 1A-3B. Return pad400 includes a backing 102 made of any material as described above thatprovides support for return pad 400. Ring electrode 106 and ringelectrode 108 are configured to form ring sensor 110. Ring sensor 110may be capacitive or resistive.

In contrast to FIGS. 3A-3B, the FIG. 4 ring electrode 106 and ringelectrode 108 are disposed in substantial vertical registry with thereturn electrode 104. Electrode 104 is disposed relative to ringelectrode 106 and 108 in a generally concentric fashion, which is alsoconfigured to enhance peel detection. The impedance measurement takenfrom ring sensor 110 is primarily a function of contact impedancebetween ring electrode 106 and ring electrode 108. Any edge peelingwould affect the measured impedance thus allowing measuring component706 (see FIG. 7) to measure this effect.

To avoid an electrical contact between return electrode 104, and ringelectrodes 106 and 108, an electrical insulator (not shown) may bepositioned therebetween to avoid any unwanted electrical connections.Any suitable insulator may be used.

Although FIGS. 1A-4 have a ring sensor 110 with ring electrodes 106 and108, FIG. 5A shows another embodiment according to the presentdisclosure which utilizes a single ring electrode 506 in ring sensor508. Return pad 500 includes a backing 102 and a return electrode 104that, as previously mentioned, may be in a capacitive or a resistiveconfiguration. A ring sensor 508 is located approximately near theperiphery of return electrode 104 and is shown as a single ringelectrode 506. Sensor interface 510 is depicted and is configured tointerface with measuring component 706 (see FIG. 7). Return electrode104 also has a return interface 512 and is configured to attached to thegenerator 702 (see FIG. 7).

A small arrow representing current is shown as current arrows 514.Although not all current is shown, the region between the outer edge ofreturn electrode 104 and ring sensor 508 can have current flowingtherebetween when contacting tissue. Measuring the impedance betweenreturn electrode 104 and ring sensor 508 can be accomplished with acontrol circuit by utilizing a common reference, e.g., a ground. Oneexample of a control circuit is shown in 5B.

By changing the behavior of current traveling between return electrode104 and ring sensor 508 impedance can be measured that relatespredominately to the contact impedance of return electrode 104 and ringsensor 508. Any reduction in skin contact of the edges around or nearreturn electrode 504 would result in an increase of measured impedance.

As mentioned above, FIG. 5B is a block diagram of a system 514illustrating the impedances associated with return pad 500 when appliedto a patient. Return pad 500 includes ring sensor 508 and returnelectrode 504. Current generator 516 is shown and provides energy.Patient 520 is depicted as a dashed-line block, and measuring component522 is shown and connects to patient 520 via ring sensor 508. Measuringcomponent 522 may be separate and distinct to current generator 516.Additionally or alternatively, measuring component 522 may be part ofcurrent generator 516. Primary body impedance 530 is a representation ofthe impedance between surgical instrument 518 and return electrode 504including the contact impedances of return electrode 504 and surgicalinstrument 518. Secondary body impedance 526 is the representation ofthe impedance between ring sensor 508 and return electrode 504 includingthe contact impedances of ring sensor 508 and return electrode 512.Measuring component 522 and current generator 516 may be referenced tothe same ground 532.

In use, if return pad 500 started to peel off of a patient, the contactimpedance of ring electrode 506 would increase also increasing thecontact impedance of ring sensor 508; thus, measuring component 522would measure an increase in impedance of secondary body impedance 526because that includes the contact impedance of ring sensor 508. Sinceimpedance measured by measuring component 522 is the addition of theimpedances of ring sensor 508, secondary body impedance 526, and returnelectrode 504, measuring component 522 will sense any change insecondary body impedance 526 which includes the contact impedances ofreturn electrode 504 and ring sensor 508. E.g., if return electrode 504starts “tenting”, measuring component 522 will also detect a rise incontact impedance of ring sensor 508 as a rise in secondary bodyimpedance 526 and communicate with the generator to compensate for theabnormality.

Measuring component 522 measures contact quality by measuring impedance.For example, measuring component 522 may utilize ring sensor 110 (seeFIGS. 1A-4) in one embodiment or ring sensor 508 (see FIG. 5A) inanother embodiment to create a test signal that conducts through apatient and/or other return pad material to measuring the contactquality. Measuring component 522 may change the frequency, voltage,wattage, amperage, and/or modulation to accomplish a measurement or maykeep any of the aforementioned properties of the signal constant.Additionally, measuring component 522 may monitor any of theaforementioned signal aspects to estimate contact quality. For example,measuring component 522 may keep the voltage of a signal constant andmay measure any changes in current to estimate contact quality. Therelationships between voltage, current, and impedance are well known.

FIG. 6A shows a block diagram of system 600 according to the presentdisclosure that includes return pad 602 with a multiple-foil capacitivereturn 604 with capacitive sensing capability. More particularly, returnpad 602 has a first return electrode 606 and a second return electrode608, which operatively couples to control component 610 via returninterface 626. Return interface 626 is represented by a small circulardot illustrating a return interface that may be adapted to returncurrent from return electrodes 606 and 608. Return electrodes 606 or 608may be made out of foil and a dielectric or other materials suitable forproviding a capacitive return. Generator 516 includes both a controlcomponent 610 and a measuring component 522. Measuring componentconnects to return electrode 606 via 622 and to return electrode 624 via608. The point where waveguide 622 connects to 606 and where waveguide624 connects to return electrode 608 may be considered to be the sensinginterface. The sensing interface is operatively coupled to generator516. In system 600, measuring component 522 is located within generator516, which is in contrast to other embodiments, such as depicted in FIG.5B. Measuring component 522 may be inside generator 516 or otherwise mayexist external to generator 516. The control component 610 producescurrent relative to ground reference 612 while measuring component 522produces a test current relative to ground reference 614. Controlcomponent 610 may utilize suitable internal software, hardware,circuitry, or some combination thereof to ensure current is properlyapplied to a patient. Additionally or alternatively, control component610 may also control suitable external hardware, software, circuitry, orsome combination thereof to generate current for electrosurgery. Forexample, an external relay (not shown) may be controlled by controlcomponent 610 to physically connect or disconnect waveguide 618 fromcontrol component 610 to increase safety.

References 614 and 612 may be electrically isolated and/or an AC powersource (not shown) may also be electrically isolated from bothreferences 614 and 612, e.g. by a transformer. Surgical instrument 616is connected to the control component 610 by a waveguide 618. Ameasuring current is produced by measuring component 522.

During use, return pad 602 is placed onto an area of skin utilizing anadhesive and/or conductive material to help secure return pad 602 to apatient's skin or to enhance electrical properties, e.g., to reducecontact impedance. When a surgeon applies surgical instrument 616 toanother part of a patient's body, the patient completes the electricalcircuit of control component 610 and may produce the desired tissueeffect, e.g., cutting, coagulation, ablation etc. The return energyflows through the first foil electrode 606 and/or the second foilelectrode 608 back to control component 610 via waveguide 620.

Generator 516 can take contact quality measurements of return pad 602 byutilizing measuring component 522. A test current can be created bymeasuring component 522 to flow from return electrode 606, throughpatient tissue, and to return electrode 608. Because return electrode606 and 608 are capacitive, the measurement current should be configuredwith proper frequency, current, voltage, and/or wattage for capacitivepurposes.

Ground references 612 and 614 may be electrically connected or isolated.For example, if references 612 and 614 were connected via a wire, then afilter (not shown) may be included at some point between returnelectrode 606 and reference 612 to filter out the measuring current.This can be accomplished by suitable technologies such as a notchfilter, a low-pass filer, a high pass filter, a band-pass filter, abuffer, or some combination thereof. For example, if measuring component522 were operating at frequency f₀ and therapeutic current wereoperating at frequency f₁ then a filter, such as a notch-filter, canattenuate frequencies at and/or near f₀ from traveling along waveguide620.

Filtering, buffer, smoothing, processing or switching can be implementedwithin measuring component 522 or control component 610 to enhance thesystem. For example, the aforementioned technologies may be used toenhance noise immunity and/or provide a more efficient and accurateimpedance measurement.

System 600 may also include an intelligence component (not shown) todetermine when an unsafe impedance measurement has been detected. Forexample, an alarm may be included within the control circuitry when thecontact impedance reaches a predetermined threshold, e.g., 100 ohms. Thealarm may also be configured to determine if an unsafe temperature riseis predicted, which will trigger the generator 516 to disconnectwaveguide 620 (and/or waveguide 620) from the current component 516. Theintelligence component may be disposed inside control component 610,inside measuring component 614, or otherwise located within generator516. The intelligence component may be implemented using suitablesoftware, hardware, software in execution, or some combination thereof.

FIG. 6B shows a block diagram of system 628 according to the presentdisclosure that includes return pad 602 with a multiple-foil capacitivereturn 604 with capacitive sensing capability. System 628 issubstantially similar to system 600; however, the sensing interface isconfigured to utilize current monitors 630 and 632. Additionally oralternatively, measuring component 522 determines contact quality ofreturn pad 602 by monitoring the difference between the return currentscoming from return electrode 606 and 608, respectively. Becauseelectromagnetic energy has an affinity for a lower impedance path, apeeling in either return electrode 606 or 608 would cause a reduction inthe current of the return electrode undergoing peeling. The reduction incurrent is the result of additional contact impedance with skin of thatparticular return electrode. The relationships between current,impedance, and voltage are well known.

FIG. 7 shows a block diagram of another envisioned system according tothe present disclosure that utilizes a return pad with a ring sensor.More particularly, system 700 includes generator 516 that has controlcomponent 610 that may generate current and measuring component 522 thatmay make contact quality measurements. A cut-off component 702 is alsoshown, which may be part of control component 610 (as shown in FIG. 7)or, alternatively, may be located elsewhere. Also, intelligencecomponent 710 is shown as part of control component 610. Intelligencecomponent 710 may, alternatively, be located within generator 516,within measuring component 522, or located elsewhere.

System 700 also includes return pad 704 that includes return electrode706 and ring sensor 708. Return electrode 706 is coupled to generator516, and ring sensor 708 is coupled to measuring component 522. Amonopolar surgical instrument 616 is shown coupled to control component610 for applying therapeutic current to a patient (not explicitlyshown).

During monopolar electrosurgery, measuring component 522 may monitorcontact quality by utilizing ring sensor 708. Intelligence component 710may analyze the information from measuring component 522. Anintelligence component may be located inside generator 516, insidemeasuring component 522, inside control component 610, or locatedelsewhere. An intelligence component, as mentioned above, can utilize arisk function algorithm to determine if an unsafe condition is reachedin return pad 704. The risk function algorithm may be a function oftherapeutic current duty cycle, therapeutic current amperage,therapeutic current settings, therapeutic current frequency, airtemperature, air humidity and air composition and/or other variablesthat affect patient and/or surgical team safety. If an unsafe conditionis reached, the intelligence component 710 communicates with thegenerator 516 to reduce current or otherwise take appropriate action,e.g., sounding an alarm. For example, intelligence component 710 maydetermine that cut-off component 702 should electrically disconnectgenerator 516 from return pad 704 and communicate a command; or cut-offcomponent may electrically disconnect return electrode 706 fromgenerator 516. Cut off component 702 may have pre-determined conditionsthat causes cut off component 702 to disconnect return electrode 706 orreturn pad 704 from generator 516, e.g., when a short occurs. Also,cut-off component may be hardware, software, software in execution,and/or circuitry, e.g., such as a microcontroller that determines that aunsafe condition is present and signals this to a relay.

Referencing FIG. 8, the present disclosure also includes a method formonitoring contact quality of a return pad of an electrosurgical systemand includes the initial step 802 of providing a return pad including abacking 102 having a top side, a bottom side, and a periphery. At leastone return electrode 104 is disposed on the bottom side of the backinglayer and is adapted to connect to a current generator. At least onering sensor 110 is disposed in substantial concentric registration withthe periphery of the backing and is configured to connect to a measuringcomponent 522 that is operable to approximate contact quality of thereturn electrode 104 during electrosurgical application. The measuringcomponent 522 is configured to communicate with the generator. Themethod also includes the steps of activating the ring sensor(s) 110 tooperatively communicate with the measuring component 522 (Step 804) andapproximating the contact quality of the return electrode 104 byanalyzing the capacitance, impedance or resistance from the ringsensor(s) 110 (Step 806). The method may also include the step ofelectrically isolating the return electrode 104 from the generator whenthe measurement component determines that a threshold condition has beenreached (Step 808).

The ring sensor(s) 110 of the providing step may include at least twopartially concentric ring electrodes 106 and 108 configured to cooperatewith the measuring component 522 to measure contact quality during anelectrosurgical procedure and communicate contact quality to thegenerator. The ring sensor 110 may also include a temperature sensitivematerial such as a positive temperature coefficient ink.

The return pad 100 (or 200, 300, 400 or 500) of the providing step mayalso include a patient interface material 116 disposed between thebacking layer 102 and skin. The patient interface material 116 isconfigured to facilitate contact quality monitoring of the returnelectrode 104 and may include a material selected from the groupconsisting of a conductive gel, a conductive adhesive, an insulatinggel, an insulating adhesive, a dielectric gel, a dielectric adhesive andan insulator.

Measurements may be taken by varying electrical parameters of a testsignal or current, e.g. voltage, frequency wattage, and/or current. Themeasurement may be made by a measuring component, e.g., measuringcomponent 522. A control component, control component 610, may beutilized to change the surgical current based upon the measurements madeby measuring component 522.

An intelligence component 710 may also be included, e.g., as part of anelectrosurgical system, to monitor the conditions of return pad in act802 and communicate the information to control component 610, to cut-offcomponent 702, and/or otherwise to other circuitry that a pre-determinedcondition has occurred. For example, if contact quality has beendegraded beyond an acceptable level, intelligence component 710 maycause an event to happen, such as sounding an alarm or by performing theelectrically isolating step. The term “electrically isolating” mayinclude disconnecting the pad from generator 516 or by utilizing cut-offcomponent 702. For example, cut-off component 702 may be a relay ortransistors that can electrically isolate the return pad in act 802 fromgenerator 516.

While several embodiments of the disclosure have been shown in thedrawings and/or discussed herein, it is not intended that the disclosurebe limited thereto, as it is intended that the disclosure be as broad inscope as the art will allow and that the specification be read likewise.Therefore, the above description should not be construed as limiting,but merely as exemplifications of particular embodiments. Those skilledin the art will envision other modifications within the scope and spiritof the claims appended hereto.

1. An electrosurgical system for measuring contact quality of a returnpad, comprising: a return pad having a backing layer, comprising: atleast one capacitive return electrode disposed on the bottom side of thebacking layer, the at least one return electrode being adapted toconnect to a return interface; and at least one ring sensor disposed onthe at least one capacitive return electrode and in substantialconcentric registration with the periphery of the at least onecapacitive return electrode, the at least one ring sensor configured toconnect to a sensing interface; a return interface adapted to returncurrent from the at least one capacitive return electrode; and a sensinginterface configured to monitor an impedance associated with the atleast one capacitive return electrode to determine contact quality. 2.The electrosurgical system for measuring contact quality of a return padin accordance with claim 1, further comprising an electrosurgicalgenerator operatively associated with the return interface.
 3. Theelectrosurgical system for measuring contact quality of a return pad inaccordance with claim 1, further comprising an electrosurgical generatoroperatively associated with the sensing interface.
 4. Theelectrosurgical system for measuring contact quality of a return pad inaccordance with claim 1, wherein the at least one ring sensor iscapacitive.
 5. The electrosurgical system for measuring contact qualityof a return pad in accordance with claim 1, wherein the at least onering sensor is resistive.
 6. The electrosurgical system for measuringcontact quality of a return pad in accordance with claim 1, wherein theat least one ring sensor includes at least two partially concentric ringelectrodes configured to cooperate with a measuring component to measurecontact quality during an electrosurgical procedure and communicatecontact quality to an electrosurgical generator.
 7. The electrosurgicalsystem for measuring contact quality of a return pad in accordance withclaim 6, wherein the at least two partially concentric ring electrodesare disposed on the at least one capacitive return electrode.
 8. Theelectrosurgical system for measuring contact quality of a return pad inaccordance with claim 1, further comprising a patient interface materialconfigured to be disposed between the backing layer and a patient'sskin, the patient interface material configured to facilitate contactquality monitoring of the return electrode.
 9. The electrosurgicalsystem for measuring contact quality of a return pad in accordance withclaim 8, wherein the interface material includes a material selectedfrom the group consisting of a conductive gel, a conductive adhesive, aninsulating gel, an insulating adhesive, a dielectric gel, a dielectricadhesive, and an insulator.
 10. The electrosurgical system for measuringcontact quality of a return pad in accordance with claim 1, wherein theat least one ring sensor includes a temperature sensitive materialconfigured to sense contact quality based upon temperature.